In general, a conventional portable electronic device receives an external input voltage through an adapter, and the adaptor is used for supplying an input voltage to the portable electronic device.
As the number of a user's portable electronic devices increases, the number of various types of adapters also increases. These adapters generally come with different electric properties including different rated input/output voltages, and a misuse of an adapter by accident may damage the portable electronic device directly. For example, a portable electronic device includes an internal circuit unit such as a battery, an electronic component and an electronic circuit, and the internal circuit unit has a maximum rated voltage equal to 12 volts. If the user uses an adapter with a voltage higher than 12 volts to supply electric power to the portable electronic device, then the battery, electronic component and electronic circuit of the portable electronic device may be damaged by the high voltage and may fail to operate.
Therefore, the present invention provides an overvoltage protection circuit to overcome the aforementioned drawbacks of the prior art.